Ernst abbe and paul rudolph



(No Model.)

E. ABBE 8v P. RUDOLPH.

PHOTOGRAPHIC OBJECTIVE.

No. 435,271. Patented Aug. 26, 1890.

lll

UNITED STATES PATENT OFFICE ERNST ABBE AND PAUL RUDOLPH, QF JENA, SAXE-XVEIMAR, GERMANY, ASSIGNORS TO CARL EEISS, OE SAME PLACE.

PH OTOG RAPHIC OBJECTIVE.

SPECIFICATION forming' part 0f Letters Patent No. 435,271, dated August 26, 1890. Application filed April l5, 1890- Serial No. 343,013. (No model.)

To all whom it may concern:

Be it known that we, ERNST ABBE, a subject of the Grand Duke of Saxe-lVeimar, and PAUL RUDOLPH, a subject of the Duke of Saxe-Altenburg, both residing at Jena, in the Grand Duchy of SaXe-Vei mar, Germany, have invented new and useful Improvements in Photographic Objectives, whereof the following is a specification.

Our invention relates to photographic objectives; and the improvement consists in the construction of a system of lenses in which the function of collecting the rays of light forming the image and that of correcting the spherical and chromatic aberration are allotted to distinct parts of the system.

In constructing` photographic objectiveglasses in which the advantage of an extended image-field is to be coupled with a large effective aperture particular difiiculties are encountered in attaining the desired degree of absence of spherical aberration of the pencils of light that produce the image. obtaining the extended field aimed at, objectives of the usual types require to be provided with lenses of high curvature, andthese always give rise to certain residual spherical aberrations, (the socalledzones,) whereby the distinctness of the image is impaired.

when the aperture is fully open. For the purpose of obviating this defect and simultaneously facilitating an improved correction ot' the chromatic aberration, we compose the objective of two uncorrected single collectinglenses, which, in view of'the aplanation of the field, have their convex or more convex sides turned outwardly and a correcting system possessing Van innite or alarge, positive, or negative focal length, so that it does not at all7 or but inconsiderably, alter the focal length of the two collecting-lenses combined, the said correcting system being constituted by two or three single lenses cemented together and arranged between and separate from the collecting-lenses. By means of this disposition it is possible to considerably diminish the aforesaid residual spherical aberration or zones. At the same time it gives a wider scope in the selection of the glasses t0 In view ofv be employed in the manufacture of the lenses composing the correcting system. In particular it furnishes favorable conditions for the application of thosekinds ot glasses which have the property of almost completely uniting three colors of the spectrum, or, in other words, which neutralize the secondary spectrum, and thus produce a superior degree of chromatic correction. The construction therei'ore yields comparatively ready means for the manufacture of such highly-achromatic obj ectives as are called apochromatic, according to the terminology introduced by Professor Abbe.

In the annexed drawing an objective carried out according to our invention is shown partly in outside view and partly in section.

L1 and L5 are t-he two collecting-lenses, made in this case of cancavo-convex form. The correcting system consists in the biconvex lens L3 and the concavo-convex dispersinglenses L2 LU the two latter being' composed of glass having such power of chromatic dispersion as is necessary to compensate the chromatic aberration of the lenses L1, L3, and L5.

According to the kinds of glass used in the construction of the described objectives, and

according to the special conditions to be real ized by the total result obtainable from the system,a perfectly symmetrical arrangement of the lenses-such as is shown by Fig. l-may in certain eases suffice. In others, where a wider range of means for corrections or for removing objectionable reflections is desired, a dissymmetrical arrangement may be preferable.

In the following tables we append three numerical exemplications of the manner in which lenses of given kinds of glass have to be ground for carrying` our inventioninto operation. In these tables the letters r1 r2 r3 fr4 T5 r6 r, rs denote the radii of curvature of the lens-surfaces marked by the said letters in the figure. d, (Z2 d3 d, d5 are the central thicknesses of the lenses, and l?, b2 the respective air distances between the lenses L1 L2 and L,l L5. All dimensions are expressed as fractions or multiples of the focal length of the entire system taken as unity. To obtain the dimensions of any particular objective, all that is necessary is to multiply the numerals given in the tables by the focal length required. The kinds of glass to which the tables refer are determined in the first 4example by the refractive indices an, nF, and

aG', corresponding to Fraunhofels spectral l lines D and F and the line Hy of the spectrum of hydrogen, respectively, whereas in the second and third examples the indices nl, and nF only are employed.

I. Symmelm'cal arrange-ment. Apoeh'romatio correclzon, (the secondary spectrum removed.)

Thi'cknesses of glass lGlasses employ/eel.

nl). 'rl/F. '7l/Gf. L1 L3 L5 .....151340 1.52457 1.52956 L2 tud L4' .1.57950 1.58745 1.59388 Position of diaphragm close behind lens L1. Largest effective aperture 0.10. Angle ot held about ninety degrees.

' Glasses employed.

nn. nGf. L1 L3 L5 1.50032 1.52037 L2 and L51 1.50303 1.53231 Position of diaphragm close behind lens L11. Largest effective aperture 0.16. Angle of field about ninety degrees. Y Ill. Symmetrcal arrangement. Aohromatz'o correction.

Thicknesses of glass Radii and air distances. T1: -fr8:0.440l d1:ol5:0.050 '72:-l7:1.3503 Cl2:cl4:0.020 r3: 115:03 v -cl3 :0.130 r11:-r5:0.2001 01:02:0.100

Glasses employed.

` n1). L1 L3 L5 .1.51730 L2andL4 ..`....'.....1.56745' Position of diaphragm close behind lens L1. Largest eective aperture 0.30. Angle o'f field about fifty degrees.

We claim as our invention- In a photographic objective, the combination of two single collecting-lenses and a oompound correcting system composed of single lenses cemented together, the said correcting system havinga large focal length and being l placed between the collecting-lenses, substantially as described.

In testimony whereof we have hereunto set our hands in the presence of two subscribing Witnesses. v ERNST ABBE.V PAUL RUDOLPH.

Witnesses:

CARL BORNGRAEBER, HENRY W. DIEDERICH.

l cm Y A, f.; lt 1s her-:ahy c'tmed that the name o the asslgnee 1u Lettel's fatemi No. 337271.? 1@ @muted Auust 26 1890,11 on the 9.3 )human 0i Emst Abb@ and Eaul Rudd )h s' y 1D O 7 y 7 5 Jana, SxQ/Vemm, Gemauy, for am in'1pr0w'*emeut iu lotogmplc Ubjecbives, was

" T" v :f-

rroueousl Wltteu and n'm'ted Culi Fe1ss7whereas sind name should have been 4 ,1 7

: f Wtten :md printed @mi Zeiss ,r and. that the Said Lettels Bant should be read. with this collectiou therein that the same may coh'm 'to the corrected files and records s gn the Gase in the Patent Oce.

'iii SWB/ counterswud alla sea-led mls .Evt-h da# o Se )tembar A. E. 1890.

-i i {SEAL} GYRUS BUSSEY, Assistcmt Secwtcwy of the Interfax C 5 Gountersgned:

-5 U. E. MTGHELL,

gj l Oomomsswner of Patents.

It is hereby oertied that the name of the assignee in Letters I )ejtent No. 435,271, of Ernst Abbe and Paul Rudolph, of

for 2bn improvement in Photographie Objeotives,77 was granted August 26, 1890, upon the application Jena, Saxe-Weimar, Germany', erroneously Written and printed Cari Feiss, Whereas said name should have been Written and printed Ocwl Zeiss and that the said Letters Patent should be read with this correction therein that the seme may conform to the corrected les and records of the ease in the Patent Office.

Signed, eountersigned, and sealed this 30th day of September, A. D. 1890.

[smh] CYRUS BUSSEY,

Assistant Secretary ofthe Interior.

Countersigned:

C. E. MITCHELL,

Oom/mission@n of Patents. 

